This invention relates to a method of connecting electrodes, and more particularly to a method of connecting a semiconductor device which is face down, using an insulating resin.
As a method of connecting a semiconductor which is face down on a circuit substrate, it is known to form a solder bump on the electrode of the semiconductor device, and to join it with the wiring electrode on the circuit substrate. In this method, since the electrode of the semiconductor device and the electrode of the circuit substrate are mechanically and electrically connected by the solder bump, when a thermal or mechanical stress acts on the semiconductor device or circuit substrate, the stress is entirely concentrated on the junction of the solder bump, possibly resulting in the breakage of the junction and the lowering of the device reliability.
To solve these problems, as shown in FIG. 1, an electrode 2 is disposed on a semiconductor device 1, and while positioning a wiring electrode 4 of a circuit substrate 3 with this electrode 2, an insulating resin is inserted between the semiconductor device 1 and circuit substrate 3, and the insulating resin is stiffened while pressing the semiconductor device 1. By making use of the contracting force of the insulating resin at the time of stiffening, the electrode 2 of the semiconductor device 1 is pressed against the wiring electrode 4 of the circuit substrate 2, thereby obtaining an electrical connection (for example, as disclosed in U.S. Pat. No. 4,749,120).
In the conventional method of fabrication shown in FIG. 1, an insulating region was placed between the electrode 2 of the semiconductor device 1 and the electrode 4 of the circuit substrate 3, and they were directly pressed together to stiffen the resin. Accordingly, an electrical connection of the two electrodes will not be obtained unless the intervening resin between the two electrodes 2 and 4 is removed, and therefore, the semiconductor device or the circuit substrate was pressed with a high pressure. As a result, a bending stress was formed on the semiconductor device or circuit substrate, and the connection between the electrodes was partially impaired, and it was difficult to obtain a favorable connection. Besides, when the pressure was high, there was a risk of destroying the semiconductor device, and this was particularly obvious in fragile devices other than silicon, such as GaAs.
Still more, since the insulating resin was applied on the entire surface of the semiconductor device 1, when the semiconductor device or circuit substrate was heated to rise in temperature, the entire insulating resin was expanded, and when this expanding force exceeded the contracting force, the electrode at the pressed part and the wiring electrode were separated from each other, which often caused a defective junction.